1. Field of the Invention
The present invention relates to a board for manufacturing a BGA (Ball Grid Array) and a method for manufacturing a semiconductor device using thereof.
2. Description of the Related Art
An IC package for a portable equipment or a small, hi-density mounting equipment has advanced in recent years. Details of these advances are described in CSP technology, and mounting material and device supporting the technology—special issue of DENSHI ZAIRYO (p.22, Set. 1998).
FIGS. 15A and 15B show a BGA using a flexible sheet 50 as an inter-poser board. FIG. 15A is a plan view, and FIG. 15B is a section view cut at A—A line.
On the flexible sheet 50, a copper foil pattern 51 is bonded by an adhesive. An IC chip 52 is fixed on the flexible sheet 50 and a bonding pad 53 is formed around the IC chip 52 with the copper foil. A solder-ball connecting pad 55 is formed through a wiring 54, which is integrated with the bonding pad 53. A solder-ball is then formed on the connecting pad 55.
In FIG. 15A, the flexible sheet 50 is indicated peripherally in solid line, and the IC chip 52 is indicated by a rectangle in solid line. At inside the bonding pads 53 formed around the IC chip 52, the solder-ball connecting pads 55 are arranged in matrix-shape.
At a rear side of the solder-ball connecting pads 55, an opening portion 57 is formed by processing the flexible sheet 50, and the solder-ball 56 is formed through the opening portion 57.
The flexible sheet 50 is used as a ceramic board and printed board, and a member is processed thinly among these boards. However a flexible sheet is expensive compared to a ceramic board and printed board. Moreover, using these boards would increase the cost of a BGA substantially including the cost to machine the opening portion 57.
Thin and lightweight types are desired for a semiconductor device used in a portable equipment and also for a BGA. However, generally the process of forming a Cu foil pattern, of mounting the IC chip 52, and of bonding wire 58 would require the use of a flexible sheet 50 as a supporting board. Therefore, the flexible sheet 50 would have to be used in view of the manufacturing processes.
Moreover, the Cu foil pattern tends to deform or peel off because the Cu foil pattern is bonded with adhesive on the flexible sheet 50. As the numbers of pads of the IC chip 52 increases year and year, making finer Cu foil patterns is needed with the BGA. Consequently, bonding area of the wiring 54 and bonding pad 53 are decreased, thereby becoming more susceptible to deformities or peeling of the Cu foil pattern.
Furthermore, manufacturing a BGA requires much time because a semiconductor manufacturer would have to inform a flexible sheet vendor on the designated pattern data, the flexible sheet manufacturer would then have to manufacture the flexible sheet, and the semiconductor manufacturer would then purchase the completed flexible sheet. Accordingly, manufacturing a semiconductor device as a product would require a considerable amount of time. The semiconductor manufacturer cannot deliver the BGA to a user in short time.
Also, heat from the IC chip 52 is insufficiently radiated because the flexible sheet 50 is interposed between the Cu foil pattern 51 and the IC chip 52.